Silica-based bioactive glasses and calcium phosphate ceramics have long been known to serve as synthetic materials useful in the promotion of bone formation in repairing bone fractures and the like. These materials are considered bioactive because they bond to bone and enhance bone tissue formation with a variable degree of success.
An estimated 11 million people in the United States have at least one medical device implant. Two types of implants, fixation devices (usually fracture fixation) and artificial joints are used in orthopedic treatments and oral and maxillofacial procedures. Approximately 80% of the fracture fixation requires adjuvant grafting. Among the joint replacement procedures an increasing number are revision surgeries with their adjuvant need for bone grafting.
Current approaches to difficult bone repair problems include utilization of autografts, allografts and synthetic grafts. Although at present auto graft material is preferentially used, there is limitation in its use, including donor site morbidity, limited donor bone supply, anatomical and structural problems and elevated levels of resorption during healing. The use of allografts has a disadvantage of eliciting an immunalogical response due to genetic differences and the risk of reducing transmissible diseases. Considerable attention has been directed to the use of synthetic materials for bone graft, most notably hydroxyapatite, tricalcium phosphate and bioactive glass. The synthetic graft material is also used to form coatings on implants, such as pins and the like, to promote attachment of new bone growth to the implement. In addition, these materials are also used as fillers in biopoloymer composites and drug delivery vehicles.